On the coast it's a safety thing. The taller softwood out here combined with heavy wet coastal snow makes for a bad combination. I've been in a helicopter flying over timber with a big fresh dump of snow on it. It was a dense stand and some of the clumps on the tree tops looked like the size of Volkswagon beetles! Getting one of those on the noggin would not be a good thing. That and sometimes just getting to work is the issue. Roads are made out of rock, and with the wet snow, makes it hard to maintain, along with steep switchbacks can make for a bit of a white knuckle drive.
Oh, and production suffers severely too!As Bob, mentioned, after a long season, guys are tired and feeling flush. Slogging through the snow at that time is a definite motivation killer.